fix : remove _{ } syntax from benchmark macro (#7822)

* commented use of common

* hack to pass tests

* another hack

* remove all commented code

* fix the easy tests

* temp hack

* follow through comma hack until better solution

* patch macro

* missed one

* update benchmarks

* update docs

* fix docs

* removed too much

* fix changes

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/offences/benchmarking/src/lib.rs

@@ -203,8 +203,6 @@ fn check_events<T: Config, I: Iterator<Item = <T as SystemConfig>::Event>>(expec
 }
 
 benchmarks! {
-	_ { }
-
 	report_offence_im_online {
 		let r in 1 .. MAX_REPORTERS;
 		// we skip 1 offender, because in such case there is no slashing